The ionic liquids as considered in the present patent application are nonaqueous salts with an ionic nature which are liquid at moderate temperatures and which result from the reaction between an organic salt and an inorganic compound,
A certain number of ionic liquids are already known. Thus, in J. Am. Chem. Soc. 101, 2, 323-327 (1979), Osteryoung et al. have demonstrated that the mixture of butylpyridinium chloride (A) and of aluminium chloride AlCl3 (B) is liquid at 40° C. over a wide range of compositions (A/B molar ratio ranging from 1/0.75 to 1/2). In Inorg. Chem. 21, 1263-1264, Wilkes et al. have shown that the compounds resulting from the reaction between AlCl3 and a dialkylimidazolium chloride, such as 1-butyl-3-methylimidazolium chloride, are liquid at room temperature, also for the same range of compositions described above. In this example of an ionic liquid, the dialkylimidazolium constitutes the cation and AlCl4 the anion. Other anions, such as nitrate, acetate or tetrafluoroborate anions, can be used (see the publication WO 9618459).
Due to their wide electrochemical window, ionic liquids can be used as battery electrolytes. They are also particularly useful in catalysis, as they are excellent solvents for organometallic compounds. Thus, for example, Patent Applications FR 2,626,572 and WO 9521806 disclose the use of the abovementioned compounds based on chloroaluminate in the alkylation, in two-phase catalysis, of aromatic or isoparaffin compounds.